'Desire: 100 of Literature's Sexiest Stories', which is launched today, includes erotic fiction from across the globe by both big name and anonymous authors.

Ms Frostrup said the stories published are "shocking, but also entertaining, immersive, seductive and downright dirty".

Malachi said that he was thrilled that his work was chosen for the anthology which also includes stories by James Joyce, Roald Dahl, and Man Booker winner DBC Pierre.

"This is a serious book with a serious editor and serious writers," he said. "Writing erotic fiction was perhaps a dangerously playful thing for me to do, but I wanted to normalise sex within story-telling.

"It is a challenge which too many novelists shirk. They will go into detail about how someone holds a tea-cup or a cigarette, but they are squeamish about describing sexual intimacy in the same way."

Malachi's story opens with a meeting between twin brothers. One suggests to the other - over lunch in a vegetarian restaurant - that they swap wives, arguing that it will be more natural and problem-free given that they once "shared a womb".

The plot progresses as the two couples visit a country house in Donegal to celebrate the brothers' birthday.

Malachi said that while the story was inspired by events in his own life, it was not autobiographical.

"I have a biological twin and I was born in Muff, Co Donegal, but this is not my story," he said.

"I have never been part of a wife-swapping group. An author can create something, without having experienced it.

"I've described murders in my fiction, but I've never killed anyone. I've written a novel in which the central character is an IRA bomber who carries out punishment shootings, yet I've never planted a bomb or fired a shot."

Malachi said that the idea for the short story came from teenage evenings at ceili dances with his twin, Roger, in west Belfast in the late 1960s.

"We used to play a game with our partners when we went to dances in the ardscoil in Divis Street," he recalled.

"There was a point, during the Waves of Tory, where Roger and I would swap places to see if the girls we were dancing with would notice.

"That wee trick that we played all those years ago was the trigger for my story, though Roger and I never swapped girlfriends or anything like that.

"I don't know what Roger makes of my story. I've posted it on my Facebook page, but he has never commented."

Malachi revealed that he has written around a dozen saucy stories, some of which have been published in the Erotic Review online magazine.

His novel, which is available on Kindle, is the recreation of the life of Judas Iscariot and includes erotica material.

Malachi said that many established writers use a pseudonym when writing erotica, but he had chosen not to.

"Some writers don't publish this material under their own names because they prefer that it's kept secret from their families and workmates," he explained.

"Maybe they want to make a distinction between their erotic writing and their other, more mainstream work.

"They fear they would be judged by their sex stories and that people would poke fun and disparage them."

Malachi, whose biography of Gerry Adams will be published by Faber next September, doesn't believe there's any conflict between his political writing and his sex stories.

"I don't think people will be shocked that I write erotic fiction," he said.

"I'm quite diverse in the things I do and I've a fairly bawdy sense of humour. These stories are a serious exercise of my imagination and I stand over them."

Malachi said that he would love to write a 'Fifty Shades of Grey'-type bestseller which would make him millions - but one with a plot.

"I didn't read Fifty Shades in its entirety but, from extracts I have seen, the language was appallingly clumsy," he claimed.

"The aim is just to sexually arouse the reader. I want my erotic fiction to be good story telling, in which the sex is well written."

Malachi said there was a gap in the market for this type of fiction.

"With the liberalisation of the law on obscenity after the publication of Lady Chatterley's Lover, more sexual writings were to be expected. But writers did not exercise their freedom," he said.